EXCEED THE SPACE PROVIDED. This five year competitive renewal proposes the continuing funding of the Mallinckrodt GCRC at Massachusetts General Hospital. The Clinical Research Center has provided continuous support for MGH investigators performing human research since 1921,with support from NCRR as a GCRC since 1978.In the previous 5 years, the GCRC has supported 190 protocols conducted by more than 200 investigators in the Departments of Medicine, Neurology, Psychiatry, Pediatrics, Orthopedics, Anesthesia, Radiology, and Surgery. The current proposal continues the wide-spread support for clinical investigation at the MGH, including 119 protocols with the majority (95%)performed by NIH supported investigators. The proposed studies include research in metabolism, neuroendocrinology, reproductive physiology and disorders of the hypothalamic-pituitary-gonadal axis, HIV, diabetes including islet transplantation, psychiatric disorders including schizophrenia, addiction, obsessive compulsive disorders and anorexia, neurologic disorders such as Huntington's disease, Alzheimer's disease and amyotrophic lateral sclerosis, and the neurologic effects of general anesthesia, among others. In addition to the established Bionutrition, Biostatistics and Bioinformatics, and Clinical Laboratory Cores, we propose a new Biomedical Imaging Core that is designed to support the increasing number of MGH and MIT investigators using NMR, PET scanning, and other imaging modalities in human research. Thirty six protocols from 26 investigators in Radiology,Anesthesia, Medicine, Psychiatry, and Neurology that will use this core are included. A formal program of education for investigators, research nurses and dietitians, medical and pre-med students remains a strong component of the current application. Currently, nine CAP or K-23 awardees are included in the grant proposal. A satellite GCRC, located at the Massachusetts Institute of Technology and which has been increasingly integrated into the MGH GCRC activities during the previous 3 years, is included in this proposal. The satellite proposal, structured as a subcontract to the MGH, includes 48 protocols that are conducted in their entirety at MIT or at both GCRCs. The collaboration between the MGH GCRC and MIT satellite extends across all aspects of the GCRC includingjoint administration, shared resources, such as the Bionutrition, Biostatistics, and Imaging Cores, and joint training to expand the research resources at both institutions and facilitate the seamless